Basically if all you are doing is bashing, then the stock TRX steel pivot balls will work just fine for the most part. The aluminum balls are the lightest, and the titanium balls are lite and super strong, but they can all fail in big hits. If keeping the wallet full is the key, then just use the steel stock pivot balls and save your money for more important things like Brushless motors and high voltage ESC's and Lipos. If you are worried about failures, then buy two sets of the stock pivot balls at the lowest price possible and you will have spares. Easy, Peasey, nice and easy $$$
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